In general, in a clutch unit using engagement elements such as cylindrical rollers or balls, a clutch part is arranged between an input member and an output member. The clutch part is configured to engage and disengage the engagement elements, such as cylindrical rollers or balls, between the input member and the output member, to thereby control transmission and interruption of a rotational torque.
The present applicant has previously proposed a clutch unit assembled to a seat lifter part for an automobile, which is configured to vertically adjust a seat through a lever operation (for example, see Patent Literature 1). The clutch unit disclosed in Patent Literature 1 includes a lever-side clutch part, which is configured to receive a rotational torque to be input through a lever operation, and a brake-side clutch part, which is configured to transmit the rotational torque from the lever-side clutch part to an output side and interrupt a rotational torque from the output side.
The lever-side clutch part mainly includes an outer ring, an inner ring, a plurality of cylindrical rollers, a cage, and two centering springs. The outer ring is configured to receive the rotational torque to be input through the lever operation. The inner ring is configured to transmit the rotational torque to be input from the outer ring to the brake-side clutch part. The plurality of cylindrical rollers are configured to control the transmission and interruption of the rotational torque from the outer ring through engagement and disengagement in wedge gaps between the outer ring and the inner ring. The cage is configured to retain the cylindrical rollers at equal intervals in a circumferential direction. The two centering springs are configured to accumulate elastic forces with the rotational torque from the outer ring, and return the cage and the outer ring to respective neutral states by the accumulated elastic forces when the input of the rotational torque is lost.
The brake-side clutch part mainly includes an outer ring, a side plate, an output shaft, a plurality of pairs of cylindrical rollers, plate springs, a cage, and a friction ring. The outer ring and the side plate are constrained in rotation. The output shaft is configured to output the rotational torque. The plurality of pairs of cylindrical rollers are configured to control interruption of the rotational torque from the output shaft and transmission of the rotational torque from the lever-side clutch part through engagement and disengagement in wedge gaps between the outer ring and the output shaft. The plate springs are configured to apply a separating force to the pairs of cylindrical rollers. The cage is configured to retain the pairs of the cylindrical rollers and the plate springs at equal intervals in the circumferential direction. The friction ring is configured to apply a rotational resistance to the output shaft.
The cage of the brake-side clutch part is formed integrally with the inner ring of the lever-side clutch part. With this, in the brake-side clutch part, the cage has a function of serving as an input member configured to receive the rotational torque to be input from the lever-side clutch part in addition to a function of retaining the pairs of cylindrical rollers and the plate springs at the equal intervals in the circumferential direction.
The friction ring is mounted and fixed to the side plate, and is configured to apply the rotational resistance to the output shaft during a lever operation by a friction force generated in a portion in contact with the output shaft. Moreover, protrusions configured to transmit the rotational torque from the inner ring of the lever-side clutch part to the output shaft are formed on the output shaft. The protrusions are respectively inserted into and arranged with a circumferential clearance in holes formed in the cage integrated with the inner ring of the lever-side clutch part.
In the lever-side clutch part, when the rotational torque is input to the outer ring through the lever operation, the cylindrical rollers are engaged with the wedge gaps between the outer ring and the inner ring. The rotational torque is transmitted to the inner ring thorough the engagement of the cylindrical rollers in the wedge gaps, thereby rotating the inner ring. On this occasion, as the outer ring and the cage rotate, the elastic forces are accumulated in both of the centering springs.
When the input of the rotational torque is lost, the cage and the outer ring return to the respective neutral states by the elastic forces of both of the centering springs while the inner ring maintains a given rotational position. Thus, the inner ring rotates in an inching manner by repetition of the rotation of the outer ring, that is, a pumping operation on an operation lever.
In the brake-side clutch part, when a rotational torque is reversely input to the output shaft by seating on the seat, the cylindrical rollers are engaged with the wedge gaps between the output shaft and the outer ring, and the output shaft is thus locked to the outer ring. In such a manner, the rotational torque reversely input from the output shaft is locked in the brake-side clutch part, and the reverse transmission to the lever-side clutch part is interrupted. As a result, the seat cannot be vertically adjusted.
Meanwhile, when the rotational torque is input from the inner ring of the lever-side clutch part to the cage of the brake-side clutch part, the cage rotates to be brought into abutment against the cylindrical rollers, and presses the cylindrical rollers against the elastic forces of the plate springs, thereby disengaging the cylindrical rollers from the wedge gaps between the outer ring and the output shaft. As a result of the disengagement of the cylindrical rollers from the wedge gaps, the locked state of the output shaft is released, and the output shaft thus becomes rotatable. When the locked state of the output shaft is released, the rotational resistance is applied to the output shaft by the friction ring.
When the cage of the brake-side clutch part further rotates, the clearance between each of the holes of the cage and each of the protrusions of the output shaft decreases, and the cage is brought into abutment against the output shaft in a rotation direction. As a result, the rotational torque from the cage is transmitted to the output shaft, and the output shaft thus rotates. In other words, when the cage rotates in the inching manner, the output shaft also rotates in the inching manner. The inching rotation of the output shaft enables the vertical adjustment of the seat.